利用PIV技术对柴油机高压喷雾流场的可视化研究

研究不同喷雾时刻及介质状态变化对柴油喷雾流场的影响.采用PIV(particle image velocimetry)激光测试技术对高压柴油喷雾流场进行速度场测量实验.实验时利用前次喷雾的液滴作为示踪粒子对当次喷雾进行速度场计算.分别进行了单次喷雾时刻、喷油压力、介质密度不同时的喷雾实验.喷雾过程中在雾注前锋周围会形成卷吸涡,且其强度随喷雾的发展及喷油压力的提高而增加;当介质密度增加后,雾注前锋贯穿速度降低,相对速度增加.柴油喷雾过程中形成的卷吸涡有利于柴油向周围空气的扩散,提高喷油压力可以有效地强化这种效果;介质密度增加使液滴密集度增加,对油气扩散混合有不利影响.

Visibilization Research in the Flow Field of High Pressure Diesel Spray by PIV Technique

To investigate the effects of the flow field by the injection time and the medium status, particle image velocimetry(PIV) technique is used. The droplets induced by the former spray are used as tracer element in current spray. The experiments include the velocity measurement of different time, injection pressure and the background density of the folw fied. A swirl forms around the tip of the spray during the course of injection and its intensity gorws up when the spray develops and the injection pressure increases. When the medium density increases, the penetration speed reduces and the relative speed increases. Thus the swirl caused by the spray is of benefit to the oil diffuseness, and increasing the injection pressure can intensify this effect. Increasing the medium density will make the drops denser and this will slow down the mixing speed of the oil and air.